Add support for macOS (Darwin) for Java and Rust

[tonyfettes]

This fixes microsoft/multilspy#28 , i.e. add support Java and Rust LSPs on macOS.

[LakshyAAAgrawal]

Dear @tonyfettes, Thank you very much for your contribution!

Kindly fill the CLA, which is a requirement for accepting the contribution, and I am very glad to merge the PR.

[LakshyAAAgrawal]

Dear @tonyfettes , Thanks a lot for making the PR. In order for me to merge the PR, I request you to kindly fill the CLA as per the instructions shared by microsoft-github-policy-service bot. Kindly let me know if there's anything I can help address regarding the same, and thank you very much for your contribution!

[tonyfettes]

@microsoft-github-policy-service agree

[AetherPrior]

@LakshyAAAgrawal could you merge?

[LakshyAAAgrawal]

Dear @tonyfettes, Thanks a lot for the PR. @AetherPrior, I will be reviewing it in a few days and will merge it soon after. Please allow me some time.